In the related art, an intake device provided with a bearing member which rotatably supports a rotating shaft of a valve body between intake ports adjacent to each other is known (refer to, for example, JP 2010-1847A (Reference 1)).
Reference 1 described above discloses an intake device which is provided with an intake device main body that includes a surge tank and a plurality of intake ports branching from the surge tank to the downstream side, a valve body provided for each of the intake ports, a rotating shaft that rotates the valve bodies, and a bearing member that is disposed between intake ports adjacent to each other and rotatably supports the rotating shaft. The valve body is configured such that, if the valve body is rotated to a closed state, the valve body comes into contact with a partition wall portion configuring an opening portion of the intake port, thereby blocking (sealing) the opening portion (the intake port). The bearing member is fitted into a bearing mounting portion of a concave shape (a cutout shape) formed in a partition wall between the intake ports of the intake device main body, thereby being fixed to the partition wall between the intake ports. The intake device main body has a structure of being divided into plural pieces, welding portions are respectively formed on a side of the upper surfaces of the bearing member and the partition wall of a first piece and a lower surface side of a second piece, and these pieces are joined to each other by welding.
Here, if the dimensional accuracy of the partition wall portion in the vicinity of the opening portion of the intake port in which the bearing member is disposed is low, sealing properties of the valve body are adversely affected, and therefore, it is very important to secure dimensional accuracy in the vicinity of the opening portion of the valve body. However, in the intake device of Reference 1 described above, a sufficient thickness is required in the partition wall portion in order to fit the bearing member into the partition wall portion (the bearing mounting portion), and on the other hand, if the partition wall portion having a thick thickness in this manner exists, a molding defect easily occurs, and therefore, there is a problem in that it becomes difficult to secure dimensional accuracy in a thick portion (a partition wall portion in which a seal surface by the valve body is formed) in the vicinity of the bearing member.
Therefore, in order to secure dimensional accuracy, it is conceivable that the partition wall portion in the vicinity of the bearing member be made to have a hollow structure, thereby thinning the wall thickness of the partition wall while maintaining the total thickness of the partition wall.
However, on the side of the upper surfaces (welding surfaces) of the bearing member and the partition wall of the first piece, it is necessary to provide a welding portion which is welded to the second piece, and therefore, it is not possible to form a hole or the like for making a hollow structure therein. As a result, in the intake device of the related art as in Reference 1 described above, the partition wall portion (the seal surface by the valve body) in the vicinity of the bearing member becomes thick in wall thickness, and thus there is a problem in that it is difficult to secure the dimensional accuracy of the seal surface.